<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>根据平均分来划分等级</title>
    <script>
        var chinese = parseFloat(prompt('请输入语文成绩'))
        var math = parseFloat(prompt('请输入数学成绩'))
        var english = parseFloat(prompt('请输入英语成绩'))
        var chemical = parseFloat(prompt('请输入化学成绩'))
        var History = parseFloat(prompt('请输入历史成绩'))

        var avg = (chinese + math + english + chemical + History) / 5
        var score = Math.floor(avg / 10)

        switch (score) {
            case 10:
                alert('优秀')
                break
            case 9:
                alert('优秀')
                break
            case 8:
                alert('良好')
                break
            case 7:
                alert('一般')
                break
            case 6:
                alert('较差')
                break
            default:
                alert('很差')
                break
        }
    </script>
</head>

<body>

</body>

</html>